Air return percussive tool



Jan. 16, 1968 R. E. POWERS 3,363,517

AIR RETURN PERCUSSIVE TOOL Filed Sept. 16, 1965 2 Sheets-Sheet 1 i exuAosT O F O 9 W I 40 7/7; 5/ 6/ K? 7i Y 6 47 66 c 4-8 k 4 ##Q INVENTOR. 5444490 5 fowsms AG /VT United States Patent 3,363,517 AIR RETURN PERCUSSIVE TOOL Richard E. Powers, Monterey Park, Califi, assignor to Powers Wire Products (30., Inc., El Monte, Calif., a corporation of California Filed Sept. 16, 1965, Ser. No. 487,774 Claims. (Cl. 91-416) This invention is concerned with a cylinder and piston motor in a percussive tool that strikes objects to drive them with a hammer action, and is particularly concerned with an air return in such a tool, it being a general object of this invention to reduce the cylinder and piston mechanism and its cooperatively related return means to the fewest number of most simply formed parts, for ease of manufacture and maintenance, and for reliable and satisfactorily predictable operation.

This invention relates generally to fluid operated tools and specifically to a pneumatic tool wherein an elastic fluid is employed to effect a percussive driving action. A cylinder and piston type motor is employed for this purpose and the use of return springs and/or difierential cylinder and piston arrangements is avoided, and in place thereof a unique air return is provided which is extremely simple in concept and which permits the use of the very simplest form of cylinder as well as piston.

In a tool of the type under consideration wherein a piston is employed to drive a blade, the percussive work stroke of the piston is effected by storing an elastic fluid under pressure at the top end of the cylinder, followed by the sudden opening of a valve means that permits the stored fluid to expand explosively, after which a return stroke of the piston must be effected. As a result, the piston is not activated until sufficient volume of compressed fluid is contained in the cylinder for effecting the percussive work stroke. In order to effect a return stroke, however, percussive action is not desirable and it is preferred that a fluid operated means be employed, thus eliminating springs and the like. However, the nature of tools of the type under consideration has heretofore been thought to require a vented single acting cylinder, in order to pass the polygonal cross-section of the driver blade, to permit flexations in the same, and to allow for Working clearances around said driver blade. To these ends, therefore, differential cylinder return means have been used, but which involve complexity. Further, compound or double acting cylinder and piston motors have been devised, but which also involve complexity, in that it is presumed that the end of the cylinder which passes the driver blade must be vented to atmosphere. It has been general practice to vent the lower end of the cylinder, in any case, for the alleged necessity of permitting freedom for the piston to move without compression of entrapped fluid. Therefore, the single acting air returns as heretofore provided are encumbered with valving means that exhausts fluid from the lower end of the cylinder and that are further encumbered with complexity in the valving means which causes the return stroke to occur.

An object of this invention is to provide a percussively operable tool wherein there is a cylinder and piston motor and wherein the piston is air returned within a primarily simple cylinder construction. That is, the cylinder of the present invention is characteristically elementary in that it involves a single straight bore open at both ends; the only special features being a seat at one end of the cylinder and ports at the other end thereof.

Another object of this invention is to provide a percussively operable tool wherein there is a cylinder and piston motor and wherein the air returned piston is of primarily simple construction. That is, the piston of the present invention is characteristically elementary in that it involves a unitary body of monoform; the only special features being a ring or seal to slideably engage with the cylinder and its coupled engagement with a driver blade.

It is an object of this invention to provide a percussively operable tool having primary forms of cylinder and piston as set forth in the two preceding objects and 'wherein an air return is effective through an air release cooperatively related to the open end of the cylinder remote from the end from which the driver blade extends. In other words, the combination of a simple cylinder, a simple piston and a valve means opening and closing one end of the cylinder results in a complete and operative device, with the driver blade extending through an ordinary bearing opening at one end of the cylinder and so as to restrict leakage surrounding said blade but not necessarily to be sealed surrounding said blade.

It is another object of this invention to provide as an alternate to the immediately preceding objective, a tool of the character described wherein the piston carries a valve means that causes charging of the air return means, in place of the cooperative action of the air release above referred to.

'It is still another object of this invention to provide an air return in a cylinder and piston mechanism of the type hereinabove referred to and wherein the snubber that arrests the driving motion of the piston is operative as a seal between the body of the device and cylinder thereof, and as a seal with the piston so as to entrap compressed fluid for effecting the return motion.

Further, it is an object of this invention to provide a percussive tool having an air return means and which takes particular advantage of phenomenon involved, such as the inherent timing of action resulting from manual operation of the release as related to pneumatic operation of the tool when released; so as to permit explosive expansion of fluid before it can be adversely affected by any retardation due to charging of the air return means, and so as to permit adequate charging of the air return means before it is humanly possible to reverse action of the air release that initiated the explosive action and percussive effect of the tool.

The various objects and features of this invention will be fully understood from the following detailed description of the typical preferred forms and applications there of, throughout which description reference is made to the accompanying drawings, in which:

FIG. 1 is a side sectional view of a typical fastener driving tool incorporating the air return construction of the present invention, FIG. 2 is an enlarged detailed sec tional view of a portion of the structure shown in FIG. 1. FIG. 3 is an enlarged detailed view of a portion of FIG. 1 and showing the parts in a different operational position. FIG. 4 is a sectional view taken as indicated by line 4-4 on FIG. 1. FIGS. 5 and 6 are enlarged detailed sectional views, similar to a portion of the structure shown in FIG. 1, FIG. 5 showing the piston in a retracted position and FIG. 6 showing the piston in an actuated position. FIG. 7 is an enlarged detailed view of a portion of the piston, showing the preferred valve means employed. FIG. 8 is a view similar to FIG. 6 and shows a second form of the invention, and FIG. 9 is a view similar to FIGS. 6 and 8 and shows a third form of the invention.

The percussively operable cylinder and piston motor and air return means therefor may be used in connection with a stapling gun and, therefore, in the drawings I have illustrated this type of tool. It is to be understood, however, that the present invention is not limited to this particular tool and may be employed in connection with any explosively operable fluid actuated motor having a cylinder and piston driving means and particularly with a '33 those coupled to slender elements such as driver blades engageable with fasteners to hammer them into Work with a single stroke.

The tool, as illustrated in the drawings, is adapted to be handled manually and involves, generally, a frame A having a body portion and a handle or grip portion 11, a head B carried by the frame A and adapted to direct fasteners into a piece of work, a magazine C for handling a supply of fasteners such as staples to be received and handled by the head, a driver blade D, a cylinder E adapted to be inserted into the frame A, an air release means F adapted to cooperate with the cylinder E and control operation of the driver blade D, a piston G adapted to reciprocably operate in the cylinder E and coupled to the driver blade D, an air return means H adapted to be charged with fluid under pressure at the end of the Work stroke, and a snubber R adapted to arrest the piston G and driver blade D and to seal with the piston G at the end of the work stroke.

The frame A carries the various elements of the tool, and is shaped to be conveniently handled by a person. The frame A involves, generally, the body portion 10 and the handle or grip portion 11. The body portion 10 is a simple elongate part having a cylinder chamber 12 extending longitudinally thereof and having a recess 14 through the head thereof at the lower end of the cylinder chamber 12 for receiving and positioning the head B.

The handle or grip portion 11 is provided to give the person handling the tool a convenient means to hold the tool and is a simple grip of ordinary construction that projects from the body 10. In practice, the grip 11 may be substantially normal to the axis of the body and may project therefrom as clearly shown in FIG. 1 of the drawings.

In structures of the type under consideration, it is common practice to provide a fluid and lubricant mist pres sure supply connection 18 at the grip 11, such as a pneumatic hose or the like, and also to include a control means I at the grip 11. It is to be understood that any suitable fluid pressure and oil mist supply can be provided without affecting the present invention. In the case illustrated the hose of the power connection 18 is attached to the grip 11 through a quick disconnect and the control means I is under control of a finger operated trigger 21.

The head B is, in effect, an extension of the body 10 of the frame A and is provided to receive and deliver fasteners such as staples to the work being acted upon by the tool. The head B is carried by the body in the recess 14 and is provided with a longitudinal guideway 22 that extends through and opens at the ends of the head B. The head B has a bottom face 23 engaged with the recess 14 and it has a front end face 25 engageable with the work.

In the particular form of the invention shown, the guideway 22 is adapted to handle fasteners or staples S that are U-shaped and formed of wire, or the like, having a pair of sharpened ends (see FIG. 4). The staples referred to are substantially elongate with straight parallel shanks joined by a curved back. It will be apparent how the guideway 22 can be proportioned so that it will readily pass the staples with clearance and will act upon the staples to guide them as they are delivered through the head B and from the tool. The guideway 22 guides the driver blade D of the tool as well as the staples S that are handled thereby.

A fastener or staple receiving opening 32 extends laterally through the head B, which opening enters the bottom face 23 of the head and opens into the passage 22 so that the staples S fed to the head B are properly guided and aligned with the passage 22 before they are engaged by the driver blade D of the mechanism.

The magazine C is adapted to handle a supply or stack of fasteners or U-shaped staples S and involves, generally, a case 35 carried by the frame A, a guide 36 within the case 35, a follower 37 adapted to advance the fasteners or staples, and a feed spring 38 yieldingly urging the follower toward the head B. The case 35 is carried by the body 10 and is an elongate part that projects laterally therefrom. The case is shell like in form and the guide 36 is a core-like part that is co-extensive with the case 35 and is carried between the side walls thereof. As shown in FIG. 4 of the drawings, the case 35 and guide 36 are shaped so that a longitudinal passage 40 is formed, which passage conforms in general configuration to the U- shaped staples S which are handled by the head.

The guide 36 enters the fastener or staple receiving opening 32 and terminates in a flat end 39 that occurs in the plane of the bottom wall of the guideway 22. The follower 37 conforms with the configuration of and is slidably carried in the passage 40 and is yieldingly urged toward the head B by the feed spring 38. Means is provided to prevent the follower 37 from entering the guideway 22. The fasteners or staples S are inserted into the magazine C through the open top thereof by simply engaging them over the guide 36 ahead of the follower 37 tensioning the spring 38. As clearly shown in FIG. 1, a spring biased latch 30 secures the follower 37 in a re tracted position when desired, thus facilitating insertion of the fasteners.

The driver blade D is essentially a slender elongate part rectangular in cross sectional configuration and terminates at its forward end in a fiat fastener or staple driving face 45, The blade D has a lower staple driving portion at the forward end thereof which occupies the guideway 22 of the head B, and the blade D has an upper driven portion 46 at the rear end thereof which couples to the piston G. As shown, the piston is slotted and there is a pin 47 that positively connects the parts for coupled engagement. In practice, the fit of the driver blade in the guideway 22 is not air-tight or leakproof, but it does afford substantial resistance to fluid flow and thereby restricts volume of leakage, especially when related to the short length of time to which said fit of parts is subjected to the return of air pressure.

The cylinder E is a sleeve structure that is inserted into the cylinder chamber 12 to reciprocably receive the piston G and in order to establish a surrounding reservoir 60 adapted to be periodically charged with fluid under pressure. In practice, the fluid reservoir 60 is an annulus established between the straight tubular cylinder wall 61 and wall 62 that forms the cylinder chamber 12. Thus, the fluid reservoir 60 occupies the circumferential area of the cylinder chamber 12, that surrounds the cylinder wall 61. In carrying out the invention, the cylinder E is a simple insert that is pressed into working position with its lowermost end seated in a recess 63 at the bottom of the cylinder chamber 12. The lowermost end of the cylinder E is normally open and is therefore open to the guideway 22. The recess 63 locates the cylinder E so that the uppermost end thereof enters a bore 62, there being a radial flange 64 at the uppermost end of the cylinder to slidably engage within the chamber bore, and there being a seal 65 at said fit, as shown. The cylinder E with its uppermost flange 64 is characterized by an upwardly faced seat 67 that is cooperatively exposed to the release means F. In the form illustrated, the seat 67 is a flat faced seat in a plane normal to the axis of the cylinder and adapted to be engaged by a flat faced and axially reciprocable valve element 69. In accordance with the invention, the cylinder E is provided with one or more openings 68 at or near the lower end of the cylinder wall 61 and/ or reservoir 60, said openings remaining in communication with the interior of the cylinder E at all times, it being significant that the piston G does not pass over or cross the opening or openings 68.

The air release means F that may be employed is disclosed in Patent No. 3,026,849 entitled, Fluid Operated Valve for Release of Fluid Under Pressure, issued Mar. 27, 1962, and is adapted to cooperate with and control operation of the piston G, later described. The means F is provided to release the piston G from the upper end of the cylinder E and to move and accelerate the piston G when sufficent fluid pressure has been established to effect the desired percussive work stroke. The release means F may involve various and suitable mechanisms to carry out the function referred to without affecting the present invention. For example, the release means F may involve means adapted to shift a valve element 69 between two positions, one where the supply of air is shut off from within the cylinder E and air exhausted therefrom, and the other where the supply of air is admitted to within the cylinder E and the exhaust is closed. The frame A is chambered in order to provide a reservoir 58 for the accumulation of a volume of air under pressure, and the valve seat 67 at the top end of the cylinder E is exposed to and opens into said chamber to be opened and closed by the valve element 69 of means F. The upper end of the reservoir 58 remote from the head B is closed by a cap 59, the release means F being carried by and operable through said cap.

The piston G operates to reciprocate in the cylinder E and has driving engagement with the driver blade D. The piston G is adapted to drive or move the driver blade D forwardly or downwardly and is adapted to be damped or snubbed at the lower extent of its travel or stroke. The cylinder chamber 12 is supplied with fluid under pressure by the valve means I, to effect the piston movement as hereinafter described. The piston G is slideably carried in the cylinder E and is actuated to retract and to advance in the cylinder. In accordance with the invention the piston G is sealed with the cylinder E and is engaged therein to have substantial frictional restraint against movement when at rest. However, when said restraint is overcome, the piston G is free to move in the cylinder E with sealed engagement with the cylinder. As is shown, a suitable seal and frictional restraining means is provided for in an O ring 70, a ring which seals the piston with the cylinder and which affords frictional resistance to piston movement when the piston is at rest. The tool illustrated is operated entirely by fluid pressure so that when the trigger 21 of the tool is operated the piston G is moved percussively toward the bottom of the cylinder E, and so that when the trigger 21 is released the piston G is air returned to the top of the cylinder E. The trigger 21 controls the valve means J later described.

The piston G is light in weight, preferably, and is characterized by its monoform disc-like configuration with its outer peripheral wall slideably engaged in the cylinder E. The piston G is essentially a solid body of material having a head portion 71 of said disc configuration and characterized by a depending body portion 72 of somewhat reduced diameter for the handling of fluid below the head portion 71 and for eflfecting the air return function. The body portion 72 is provided with a downwardly disposed face 73 preferably in a plane normal to the piston axis, and it is this body portion 72 and face 73 which pass the opening or openings 68 in the cylinder wall 61 for purposes to be later described. And, as above pointed out, the piston G is slotted at 48 to receive the driven portion 46 of the driver blade D secured by the pin 47, said slot being formed in a centered part of reduced diameter depending below the body portion 72.

The valve means I is a fluid pressure exhausting means that retains or exhausts operating fluid, air and oil mist, in or from the release means F. The valve means I is preferably formed in and carried by the frame A of the tool and, as shown is a three way valve with a port 90 opening into the pressure chamber, a port 91 open to atmosphere, and a port 88 opening beneath a piston that lifts the valve element 69 of means F. A manually oper able trigger 21 operates a valve 85 to open port 90 to port 88, whereby the valve element 69 of means F is lifted. The said valve element of means I is normally closed, being vented to atmosphere through port 91.

In accordance with the invention the cylinder E and piston G are of simple uncomplicated construction as above described, the piston being normally restrained from moving but subject to freedom of movement when said movement is initiated, the cylinder being seated as by a light press fit to seal within the cylinder chamber 12 so as to establish the air return reservoir 60. With the tool thus far described, I provide the air return means H which is primarily comprised of means to charge the air return reservoir at or toward the end of the work stroke cycle or period of operation. To this end the means H involves porting of air into said return air reservoir 60 so that the build up of pressure occurs only toward the end of the percussive work stroke period of the tool. By so doing, resistance to acceleration of the piston G does not adversely afiect the percussive action of the tool and build-up of resistance toward the end of the percussive work stroke is advantageously employed to damp the motion of the piston G and driver blade D. As hereinabove pointed out, leakage out of the cylinder chamber 12 through the guideway 22 is of little matter, providing a reasonably tight though free mechanical fit prevails, the return means H having a scaling function that entraps air under pressure within the reservoir 60 independent of the cylinder and driver blade exit structure.

The snubber R is provided for its usually expected function of stopping the piston G and the attached driver blade D, and additionally is provided to seal the reservoir 60 during the short period of time when the piston G and driver blade D are at the lower end of the work stroke. Accordingly, the snubber R is a circular part that surrounds the driver blade D and that engages and seals with the wall 61 of the cylinder, and which is made of the usual rubber or like material and is formed to provide a seat upon which the piston body portion 72 is adapted to have flat sealed engagement. It is at this period and point of engagement that the disc portion 71 is held above the opening or openings 68 for the access of fluid pressure to the under side of the disc portion 71.

The air return means H can be employed in several or more forms, three of which are illustrated in the accompanying drawings. All three forms of the air return means H involve air restriction means charging the reservoir 60 with air under pressure from the discharge of compressed air into the cylinder E that effects the percussive work stroke of the piston G and attached driver blade D. Time is necessarily involved for the piston G and driver blade D to travel the length of the cylinder E and during this interval of time the compressed air is exposed to ports 100, 101 and 102 in the three separate forms illustrated. In the preferred form shown in FIGS. 1 to 7 the port (or ports) is of generous capacity and restriction of flow is accomplished by the provision of a biased check valve 105. The form and location of this valve can vary as circumstances require and it is preferably carried on the piston body portion 72, in a groove seat surrounding the same, and in the form of an elastic O ring that can be forced to expand and release fluid from a central passage opening at the top of the piston, and that can seat so as to check reverse flow. Thus, the valve restricts and/ or retards fluid flow, and upon impact of the piston body 72 with the seat 75 to have sealed engagement therewith, the valve 105 assuredly yields so as to permit charging of the reservoir 60. The human element enters into this timing procedure. In the event that the person operating the tool holds the trigger 21 longer than the time interval of operation of the piston G and driver blade D to the actuated positions, and this is usually the case, then there is an overlap in timing which assures adequate charging of the reservoir 60.

In FIG. 8 of the drawings I have shown a second form of the invention wherein the ports 101 are restricted orifices that restrict the flow of fluid in charging the reservoir 60. Again, time is involved during the percussive work stroke cycle, and the size of the orifice ports 101 is regulated so as to amply charge the reservoir 50 in order to effect the return of the piston G and driver blade D. As shown, the ports 101 are carried in the piston G so as to be open to the interior of cylinder E and to charge the reservoir 6% through the cylinder openings 68.

'In FIG. 9 of the drawings I have shown a third form of the invention wherein the ports 102 are restricted orifices as above described, carried by the cylinder In this embodiment the ports 102 extend through the flange 64 of the cylinder to open at the seat 67 thereof, whereby the said ports 102 are closed and/ or exposed by action of the valve element 69 of the air release means F.

From the foregoing it will be apparent that the present invention provides an air return in a percussively operated tool, and wherein the charging of said air return does not hinder or adversely affect the striking action of said tool. On the contrary, the build-up of air return pressure in the reservoir 60 is controlled so as to occur at or during the end of the work stroke where this buildup is advantageously employed to arrest the inertia of moving parts. Thus, by restricting the fluid flow during the initial periods of operation, there is no adverse effect to hamper the normally expected and desired acceleration of the piston G and driver blade D,

Having described only typical preferred forms and applications of my invention, 1 do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any modifications or variations that may appear to those skilled in the art and fall within the scope of the following claims.

Having described my invention, 1 claim:

1. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder with a piston operable therein between a retracted position at one end of the cyliner and an actuated position at the other and closed end of the cylinder, and with a driver extended from the piston and through a close fitting limited leakage guideway at the said other closed end of the cylinder;

(b) means operable to charge and to exhaust the cylinder at said one end thereof;

(c) restraining means normally holding the piston at rest at said retracted position;

(d) a closed fluid reservoir in open and continuous communication with the cylinder below the piston throughout its travel between said retracted and actuated positions;

(e) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting port through the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir below the piston when the first mentioned means is operated to charge the cylinder;

(f) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

2. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder with a piston operable therein between a retracted position at one end of the cylinder and an actuated position at the other and closed end of the cylinder, and with a driver extended from the piston and through a close fitting limited leakage guideway at the said other closed end of ,the cylinder;

(b) means operable to charge and to exhaust the cylinder at said one end thereof;

(c) restraining means normally holding the piston at rest at said retracted position;

(d) a closed fluid reservoir in open and continuous communication with the cylinder below the piston throughout its travel between said retracted and actuated positions;

(e) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting check valve means through the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir below the piston when the first mentioned means is operated to charge the cylinder;

(f) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

3. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder with a piston operable therein between a retracted position at one end of the cylinder and an actuated position at the other and closed end of the cylinder, and with a driver extended from the piston and through a close fitting limited leakage guideway at the said other closed end of the cylinder;

(b) means operable to charge and to exhaust the cylinder at said one end thereof;

(0) restraining means normally holding the piston at rest at said retracted position;

(d) a closed fluid reservoir in open and continuous communication with the cylinder below the piston throughout its travel between said retracted and actuated positions;

(e) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a port through the piston and communicating with the fluid under pressure advancing the piston, a valve seat surrounding the piston and carrying a constricted check valve element to yieldingly open the port into the cylinder below the piston and into said reservoir when the first mentioned means is operated to charge the cylinder;

(f) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

4. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder with a piston operable therein between a retracted position at one end of the cylinder and an actuated position at the other and closed end of the cylinder, and with a driver extended from the piston and through a close fitting limited leakage guideway at the said other closed end of the cylinder;

(b) means operable to charge and to exhaust the cylinder at said one end thereof;

(c) restraining means normally holding the piston at rest at said retracted position;

(d) a closed fluid reservoir in open and continuous communication with the cylinder below the piston 9 throughout its travel between said retracted and actuated positions;

(e) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting port in open and continuous communication with the reservoir above the piston throughout its travel between said retracted and actuated positions and thereby communicating with the fluid under pressure advancing the piston and open into said reservoir when the first mentioned means is operated to charge the cylinder;

(f) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

5. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder with a piston operable therein between a retracted position at one end of the cylinder and an actuated position at the other and closed end of the cylinder, and with a driver extended from the piston and through a substantially close fitting limited leakage guideway at the said other closed end of the cylinder;

(b) means operable to charge and the exhaust the cylinder at said one end thereof;

(c) restraining means normally holding the piston at rest at said retracted position;

(d) a snubber means comprising a body of resilient material surrounding the driver and with a seat having sealed engagement with the bottom of the piston upon arrestnient of the piston at said actuated position;

(e) a closed fluid reservoir in open and continuous communication with the cylinder above said snubber seat and below the piston throughout its travel between said retracted and actuated positions;

(f) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting port through and opening above the bottom of the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir when the first mentioned means is operated to charge the cylinder;

(g) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

6. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder with a piston operable therein between a retracted position at one end of the cylinder and an actuated position at the other and closed end of the cylinder, and with a driver extended from the piston and through a substantially close fitting limited leakage guideway at the said other closed end of the cylinder;

(b) means operable to charge and to exhaust the cylinder at said one end thereof;

(c) restraining means normally holding the piston at rest at said retracted position;

(d) a snubber means comprising a body of resilient material surrounding the driver and with a seat 10 having sealed engagement with the bottom of the piston upon arrestment of the piston at said actuated position;

(e) a closed fluid reservoir in open and continuous communication with the cylinder above said snubber seat and below the piston throughout its travel between said retracted and actuated positions;

(f) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting check valve through and opening above the bottom of the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir when the first mentioned means is operated to charge the cylinder;

(g) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

7. In combination: (a) a single stroke fluid pressure operated motor hav- (b) means operable to charge and to exhaust the cylinder at said open end thereof, from fluid pressure stored in said cylinder chamber;

(0) restraining means normally holding the piston at rest at said retracted position;

(d) a closed fluid reservoir surrounding the cylinder and in continuous communication with the cylinder through an opening therein below the piston throughout its travel between said retracted and actuated positions;

(e) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting port through the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir below the piston when the first mentioned means is operated to charge the cylinder:

(f) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

8, In combination: (a) a single stroke fluid pressure operated motor having a cylinder chamber with an open ended cylinder seated therein to reciprocably receive a piston operable between a retracted position at said open end of the cylinder and an actuated position at the other seated and closed end of the cylinder, and with a driver extended from the piston and out of the seated and closed end of the cylinder and through a close fitting limited leakage guideway in said cylinder chamber;

(b) means operable to charge and to exhaust the cylinder at said open end thereof, from fluid pressure stored in said cylinder chamber;

(c) restraining means normally holding the piston at rest at said retracted position;

((1) a closed fluid reservoir surrounding the cylinder and in continuous communication with the cylinder through an opening therein below the piston throughout its travel between said retracted and actuated positions;

(e) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting check valve means through the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir below the piston when the first mentioned means is operated to charge the cylinder;

(f) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the build-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

9. In combination:

(a) a single stroke fluid pressure operated motor having a cylinder chamber with an open ended and ex ternally flanged cylinder seated therein to reciprocably receive a piston operable between a retracted position at said open and flanged end of the cylinder and an actuated position at the other seated and closed end of the cylinder, and with a driver extended from the piston and out of the seated end of the cylinder and through a substantially close fitting limited leakage guideway in said cylinder chamber;

(b) means operable to charge and to exhaust the cylinder at said open and flanged end thereof, from fluid pressure stored in said cylinder chamber;

to) restraining means normally holding the piston at rest at said retracted position;

(d) a snubber means comprising a body of resilient material surrounding the driver and with a seat having sealed engagement with the bottom of the piston during its arrestment at the actuated position;

(e) a closed fluid reservoir defined by the seated end and flanged end of the cylinder engaging the cylinder chamber and in open and continuous communication with the cylinder through an opening therein above 12 said snubber seat and below the piston throughout its travel between said retracted and actuated positions;

(f) and air return means for movement of the piston from said actuated position to said retracted position when the first mentioned means is operated to exhaust the cylinder and comprising, a fluid restricting port through and opening above the bottom of the piston and communicating with the fluid under pressure advancing the piston and open into said reservoir when the first mentioned means is operated to charge the cylinder;

(g) whereby there is a build-up of fluid pressure in the reservoir as the piston reaches the said actuated position, and whereby the built-up fluid pressure is applied to the piston and returns the same to the retracted position when the first mentioned means is operated to exhaust the cylinder followed by exhaust of said built-up pressure through said limited leakage guideway.

10. The single stroke fluid pressure operated motor as set forth in claim 4 and wherein the means operable to charge and to exhaust the cylinder comprises, a seat surrounding an opening into the cylinder at said one end thereof, and a valve element normally engaged upon and movable from the seat to release fluid through the opening and into the cylinder, and wherein the said fluid restricting port of the said air return means is at said one end of the cylinder and disposed beneath said valve element and opened thereby when the valve element is moved from the seat.

References Cited UNITED STATES PATENTS 1,494,030 5/ 1924 Slater 91-399 2,703,558 3/1955 \VilcoX 91-416 2,983,922 5/1961 Juilts 91-399 3,027,875 4/ 1962 Spencer 914 17 3,106,075 12/1964 Powers 91-422 3,188,921 6/1965 Bade 91-417 3,195,418 7/1965 Zukas 91-416 3,200,716 8/1965 Le Sage 9l417 3,205,787 9/1965 Volkmann 91-399 MARTIN P. SCHWADRON, Primary Examiner.

PAUL E. MASLOUSKY, Examiner.

P. T. COBRIN, Assistant Examiner. 

1. IN COMBINATION: (A) A SINGLE STROKE FLUID PRESSURE OPERATED MOTOR HAVING A CYLINDER WITH A PISTON OPERABLE THEREIN BETWEEN A RETRACTED POSITION AT ONE END OF THE CYLINDER AND AN ACTUATED POSITION AT THE OTHER AND CLOSED END OF THE CYLINDER, AND WITH A DRIVER EXTENDED FROM THE PISTON AND THROUGH A CLOSE FITTING LIMITED LEAKAGE GUIDEWAY AT THE SAID OTHER CLOSED END OF THE CYLINDER; (B) MEANS OPERABLE TO CHARGE AND TO EXHAUST THE CYLINDER AT SAID ONE END THEREOF; (C) RESTRAINING MEANS NORMALLY HOLDING THE PISTON AT REST AT SAID RETRACTED POSITION; (D) A CLOSED FLUID RESERVOIR IN OPEN AND CONTINUOUS COMMUNICATION WITH THE CYLINDER BELOW THE PISTON THROUGHOUT ITS TRAVEL BETWEEN SAID RETRACTED AND ACTUATED POSITIONS; (E) AND AIR RETURN MEANS FOR MOVEMENT OF THE PISTON FROM SAID ACTUATED POSITION TO SAID RETRACTED POSITION WHEN THE FIRST MENTIONED MEANS IS OPERATED TO EXHAUST THE CYLINDER AND COMPRISING, A FLUID RESTRICTING PORT THROUGH THE PISTON AND COMMUNICATING WITH THE FLUID UNDER PRESSURE ADVANCING THE PISTON AND OPEN INTO SAID RESERVOIR BELOW THE PISTON WHEN THE FIRST MENTIONED MEANS IS OPERATED TO CHARGE THE CYLINDER; (F) WHEREBY THERE IS A BUILD-UP OF FLUID PRESSURE IN THE RESERVOIR AS THE PISTON REACHES THE SAID ACTUATED POSITION, AND WHEREBY THE BUILT-UP FLUID PRESSURE IN APPLIED TO THE PISTON AND RETURNS THE SAME TO THE RETRACTED POSITION WHEN THE FIRST MENTIONED MEANS IS OPERATED TO EXHAUST THE CYLINDER FOLLOWED BY EXHAUST OF SAID BUILT-UP PRESSURE THROUGH SAID LIMITED LEAKAGE GUIDEWAY. 